If any of the winners are reading this and still have the tracks, I'd really appreciate if you could upload them.

The tracks are still available for download via a password-protected section of Nifflas' website. But, since Nifflas is OK with it, I will happily upload them elsewhere and post the link in this threadů if someone can give a brief description of what the competition entails, and a list of the correct answers!

First 5 people to send in a correct set of guesses get an EP containing loads of alternative Figure Space/Minifigure/Tinyfigure tracks. There's 10 paintings in question whose origin games must be guessed. Here's a partial attempt:

Not sure what this is. NightSky? Clearly it was created somewhere around his "photorealistic" stage.

This is a secret from Knytt Underground itself.

Fire Nuclear Crocodile Killer. The Area 5 tileset, to be specific.

The pinball minigame from Saira.

No clue. I'm guessing this is one of Niff's more obscure games.

This is the hidden "Evil" minigame from Knytt.

A built-in photorealistic tileset from Knytt Stories.

This is the secret game from Within a Deep Forest that showcases all the unused creatures made for it.

In order to participate in this competition, you had to find the Robo Fairy museum in Knytt Underground. There are a total of three different rooms in Chapter 3 that all lead to a hidden room connecting them for fast-travel purposes. But this room also contains the museum's hidden entrance. On its third floor, a bunch of cropped screenshots from Nifflas' games can be found. The competition required you to guess which games they're from.

Figuring this out took me several hours. Originally, I was fairly confident in most of them, but as it turns out, many of the screenshots are from particularly obscure parts of the games that sometimes have a nonstandard art style. But now I'm pretty sure I have them all figured out. I was able to locate all of the visual elements depicted in them in their respective games. I even found the exact locations of some of them.

#0: #Modarchive Story (Music Madness)#1: Operator Status XH (The credits level)#2: Within a Deep Forest (The minigame Hidden)#3: Knytt (Evil-Ville's Secret Game)#4: Knytt Stories (Waterfall Mountains in Gustav's Daughter)#5: NightSky (Both versions of Level 1 in Slightly Nonsense) (This one was really evil. Both #1 and #6 closely resemble NightSky's normal art style, yet aren't from it. This screenshot looks nothing like most of the game, yet is indeed from it.)#6: Saira (The pinball minigame)#7: FiNCK (Area 5)#8: The Great Work (The part with the tulips in the Dew Mines)#9: Knytt Underground (The Black Hole secret in Chapter 1)

Note that I gave them the same numbers as their file names (which also happens to be the chronological order of their games, with exception of The Great Work).

kilicool64's answer seems to be entirely correct! The Great Work was completed prior to Knytt Underground even though it was released afterwards, which is probably the reason for the numbering. canteven gets bonus points for including pictures.